Fixes paragraph splitting on some sites

Fixes sites with paragraphs like this:
```
<p>Quae sequuntur igitur? Zenonis est, inquam, hoc Stoici.</p>
<p>Eadem nunc mea adversum te oratio est. Ubi ut eam caperet aut quando?</p>
<p>Quid ad utilitatem tantae pecuniae?</p>
```

Because there's no spaces at the beginning or end of those paragraphs (before the `</p>` and after the next `<p>), `getSelectedText()` doesn't split it properly and it ends up showing the words `Stoici.Eadem` and `quando?Quid`.

There's probably a better solution to this, something that lets the `cloneContents()` grab the newlines between the tags as well?

Anyways, lovely bookmarklet, thanks for making it!